The missile reached as high as 151 kilometres (94 miles) over South Korea's Baengnyeong island in the Yellow Sea near the inter-Korean sea border before it disintegrated into some 20 pieces.

The rocket started breaking up before it reached its maximum altitude, Major General Shin Won-Sik told journalists.

"As it was coming down to earth, it went through another explosion," he added.

Debris fell over a wide area, about 100 to 150 kilometres west of Pyeongtaek City, he said, adding no damage has been reported.

North Korea has said the rocket would place a satellite in orbit for peaceful research purposes, but Western critics see the launch as a thinly veiled ballistic missile test, banned by United Nations resolutions.